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Bug 1967605 - Enable interrupt based asynchronous page fault mechanism by default
Summary: Enable interrupt based asynchronous page fault mechanism by default
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Enterprise Linux 9
Classification: Red Hat
Component: qemu-kvm
Version: 9.0
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: beta
: ---
Assignee: Vitaly Kuznetsov
QA Contact: liunana
URL:
Whiteboard:
Depends On:
Blocks: 1967603
TreeView+ depends on / blocked
 
Reported: 2021-06-03 13:09 UTC by Vitaly Kuznetsov
Modified: 2021-12-07 22:12 UTC (History)
8 users (show)

Fixed In Version: qemu-kvm-6.0.0-7.el9
Doc Type: Enhancement
Doc Text:
Clone Of: 1967603
Environment:
Last Closed: 2021-12-07 22:10:18 UTC
Type: Feature Request
Target Upstream Version:
Embargoed:
pm-rhel: mirror+

Attachments (Terms of Use)

Description Vitaly Kuznetsov 2021-06-03 13:09:31 UTC 
+++ This bug was initially created as a clone of Bug #1967603 +++

RHEL-8.4 disabled traditional asynchronous page fault mechanism and added a new one (interrupt based asynchronous page fault) which can be enabled with 'kvm-asyncpf-int' CPU option. The new mechanism is, however, not enabled by default as upstream QEMU supports kernels which don't have it. Downstream, we should be good as RHEL kernels starting with 8.4 have the required bits.
Comment 3 liunana 2021-07-05 11:14:54 UTC 
Test Environments:
    intel-whitley-02.khw1.lab.eng.bos.redhat.com
    qemu-kvm-6.0.0-7.el9.x86_64
    5.13.0-0.rc7.51.el9.x86_64

Test steps:
1. Boot guest with '-machine pc-q35-rhel8.5.0', check guest's dmesg.
# dmesg | grep async
dmesg | grep async
[    0.019210] kvm-guest: setup async PF for cpu 0
[    0.186264] kvm-guest: setup async PF for cpu 1
[    0.189262] kvm-guest: setup async PF for cpu 2
[    0.192261] kvm-guest: setup async PF for cpu 3
[    0.196260] kvm-guest: setup async PF for cpu 4
[    0.198263] kvm-guest: setup async PF for cpu 5
[    0.201260] kvm-guest: setup async PF for cpu 6
[    0.204260] kvm-guest: setup async PF for cpu 7

2. check 'Hypervisor callback interrupts' inside guest.
# grep Hyp /proc/interrupts
grep Hyp /proc/interrupts
HYP:          1          1          1          1          1          1          1          1   Hypervisor callback interrupts


3. check 'Hypervisor callback interrupts' inside guest while using the swap on host.
On host:
]# free -h
               total        used        free      shared  buff/cache   available
Mem:            31Gi       8.1Gi        22Gi       1.0Mi       119Mi        22Gi
Swap:           15Gi       9.2Gi       6.4Gi

Inside guest.
# grep Hyp /proc/interrupts
HYP:          1          1          3          1          1          1          1          1   Hypervisor callback interrupts




Move to verified according to above tests, thanks.


Best regards
Liu Nana
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